Primary Gastric Invasive Micropapillary Carcinoma: A Case Report.

Invasive micropapillary carcinoma is a recently identified neoplasm. A 77-year-old-female was admitted to the hospital due to progressive loss of weight and nausea. Endoscopic biopsy of the antral/prepyloric located mass was diagnosed as moderately differentiated adenocarcinoma. Subtotal gastrectomy and regional lymph node resection were performed. The tumor was composed of moderately differentiated cells arranged in micropapillary structures with only a few poorly formed glandular foci in lamina propria. Immunohistochemically, neoplastic cells of micropapillary and focal conventional adenocarcinoma areas were diffusely positive for pancytokeratin, cytokeratin 7 and epithelial membrane antigen. In micropapillary areas, membranous and peripheral cytoplasmic positivity with epithelial membrane antigen in outside of the cell clusters called "inside-out polarity" pattern that is characteristic for invasive micropapillary carcinoma were seen. Invasive micropapillary carcinoma is very rare in the stomach in the English literature.